The present invention relates generally to image data processing, interpretation and quantification of animal digit conformation for medical diagnostic purposes and more particularly to a technique for deriving special biomechanical parameters that describe the animal digit (hoof and lower leg) from images for the purpose of comparison or scoring the conformation of the bone and hoof and their spatial relationship.
An animal hoof and especially an equine hoof is composed of a relatively hard outer surface, a sole and other structures on the ground surface of the foot. The outer surface continues to grow during the animals lifetime (similar to the human fingernail). . In the wild, the growth rate of the hoof wall is approximately balanced by the wear processes as the animal moves. However, in a domestic horse, for example, such is not the case. Due to the use we humans make of the horse and the surfaces and conditions they are kept in, some ‘artificial’ treatment of the hoof is generally required. Most generally, a farrier will trim the hoof and apply a metal shoe to protect the foot. In some situations, shoes are not required, but nevertheless it may be important to trim the outer shape of the hoof from time to time.
When the farrier trims the outer shape of the hoof, a large number of choices can be made concerning what the optimal shape of the hoof might be. Over the years, a great many theories, methodologies, and opinions concerning the best shape of the hoof have been and continue to be espoused. It is generally agreed that various angles, distances, thicknesses, and other measures of the hoof shape dramatically affect the motion, comfort, and, ultimately, health of the animal such as a horse. In perhaps a somewhat typical current practice, a farrier attends to a horse about every 6 weeks. The old shoes are removed, the hoofs are trimmed, and new shoes are placed on the feet.
A typical situation for domestic horse is that the ‘toe’ portion of the hoof grows out more quickly than the ‘heel’ portion of the hoof, and hence, without periodic trimming, the angle the foot makes with the ground (as seen from a side view) would gradually change. However, a great variety of other situations concerning the shape and growth of the hoof occur, and it is the job of the farrier, sometimes with a veterinarian's advice, to determine the best course of action to maintain the health and usefulness of the horse. The use of radiographs is typical in the diagnosis of lameness problems in animals, for example, horses. Many veterinarians employ portable X-ray machines in their practice. Generally, the veterinarian takes several radiographs of a horse as part of a “pre-purchase” check-up when horses are purchased. While radiographs of all parts of the horse may be taken, there is a strong concentration in the area of the feet and lower legs. A typical radiographic study of a single foot may comprise five or more separate ‘views’ of the foot. By ‘view’, it is meant a certain positioning of the X-ray emitting machine and X-ray sensitive film. A radiograph of the equine foot from any of these views will show bone structures interior to the foot, and will often (depending on details of exposure lengths and X-ray intensity) also show the shape of the hoof wall.
Often radiographs are employed to look for problems such as bone fractures, loss of bone, addition of bone (calcifications), lesions, and other pathologies. Another use of radiographs is in looking for various physical measurements such as the thickness of the sole of the foot, the thickness of the hoof wall, the angle that a certain bone makes relative to the hoof wall, and so on. However, these radiographs are generally ‘unscaled’ so that physical measurements of length are uncalibrated and only approximate.
Due to the typical apparatus used in taking radiographs, interpreting the true lengths of features in the image is non-trivial. Because the X-ray generator is essentially a point-source of X-rays, and because the X-ray sensitive film is placed on the opposite side of the subject from the X-ray source, a ‘magnification’ effect is apparent in radiographs. That is, the image of an object in a radiograph is larger than the actual object. The exact value of this magnification effect depends upon placement of the X-ray source relative to the subject and to the X-ray sensitive film. Radiographs also display a certain form of distortion due to the fact that the X-rays are in the form of diverging rays from a point-source and due to the fact that the subject is not ‘thin’ but generally has significant depth in the direction aligned with the X-rays. This distortion is minimal near the center of the radiograph (towards which the X-ray beam was pointed) and is maximal near the outer edges of the radiograph. For this reason, veterinarians use the practice of centering the most important item in the radiograph's field of view.
A radiograph can be extremely helpful to a farrier, as the extent to which a hoof can and should be trimmed has a relationship with thickness of the hoof wall and sole, and the location of the bones of the equine digit. Because a good radiograph shows these elements, it can be invaluable as a guide to trimming the hoof. The expense of radiographs generally prohibits their use with every routine trimming, but in horses with particular problems, or those of particular value, radiographs are sometimes taken in association with a visit by the farrier to trim the hoof. As an alternative or in addition to radiographs, photographs may also be employed to record the state of the exterior shape of the hoof. Side view, front view, and solar view photographs will show many important angles and lengths which, when taken together, describe the conformation of the hoof. Again, such images are generally unscaled, so that deriving length measurements from them is difficult.
Similarly, in addition to radiographs and photographs, other imaging techniques can and are used to record and study the conformation of horses and other animals. Such techniques include MRI scans, CAT scans, ultrasound imaging, thermography, and others. Both X-ray machines and cameras (for photography) are undergoing rapid technological change from analog devices to inherently digital devices. In either case, it is now possible to obtain a digital image. The digital image may be produced directly by the camera, or obtained in a second step by ‘scanning’ the image with some kind of optical device, which can then output a digital image.
Thus, there is a need for the direct comparison in a numerical, quantitative sense between two animals such as two horses, or between one animal and a set of other like animals. There is also a need for the direct quantitative tracking of change for a given animal such as a horse over time. Finally, there is a need for the ability to summarize the overall conformation of the animal hoof and leg in the form of a single quantitative score in a well-defined way.
Therefore, it would be desirable to have images that are “scaled”, whereby these quantified and calibrated images may be compared to a predetermined database of certain information and checked against a rules based database to determine the initial physicality of a given subject. It would be further desirable to reference this data in order to compare and determine the progression of that particular subject's condition.